If you are struggling with IMToD wait until you get to Nobody's Fault But Mine (NFBM).
IMToD - I used to think it was something like instant traces too but in issue 149 of Classic Rock magazine Barney Hoskins wrote about Physical Graffiti and IMToD stating: "...complete with a reference to R&B singer Benny Spelllman's hit Lipstick Traces (on a cigarette): "I must have did somebody some good, yeah/Oh, I believe I did/I see the smiling faces/I know there must be lipstick traces, oh God..."
The Ocean has a difficult line too which I'm convinced is "I've got a date I can't be late for the hell I'm heading for". Houses of the Holy did come with lyrics but that difficult line was deliberately transcribed incorrectly to avoid the reference to hell but I can't remember where I got that bit of info from.
If you are working on a definitive lyric book with every oooh and ahhh, you may find an article in Tight But Loose issue 23 of interest. It's a deep dive into the lyrics of Led Zeppelin using software to isolate everything including studio chat and so on. The motive of the writer was "...I've always been fascinated by the Zeppelin lyrics. A few years ago, I went through the process of attempting to transcribe them, as the available ones, I feel, have errors".
Finally back to NFBM. This is not a lyric observation but a content comment. I was watching a 1955 film called "The Man with the Golden Arm" starring Frank Sinatra as a drug addict. During the half hour I was watching there were numerous references by Sinatra's character about the monkey on his back i.e. his addiction to heroin and in one scene where he's getting his injection too it gets a few mentions! With Plant also referencing - possibly - a gong or bong, all this reinforces the drug themed lyrics. As does For your Life.